1. Field of the Invention
The present invention is broadly concerned with an inking assembly adapted for mounting on a web or sheet-fed printing press of the type including a multiple-roller inking train. More particularly, it is concerned with such an inking assembly making use of a shiftably mounted, reciprocal ink ejector for delivering precise quantities of ink to at least one ink-receiving roller as the ejector assembly traverses the roller. In this manner, the use of conventional ink fountains, fountain rollers and associated adjustable inking keys is completely eliminated.
2. Description of the Prior Art
In the printing of copy it frequently occurs that the ink requirements across the width of the copy are not the same column by column or zone by zone. In some of the column positions there may be heavily pigmented areas as, for example, a half tone illustration with a dark background. This situation would require more ink to be fed in that column, as compared with other columns or zones across the copy which are only lightly pigmented, or have no printed areas of a particular color.
In order to accommodate these differential ink requirements, printing presses have long been provided with adjustable inking systems. These typically include an inking train made up of a number of rollers including an inking fountain roller, and ductor and distribution rollers. In addition, such presses include an adjustable fountain doctor blade which can be adjusted zone by zone along the length thereof by means of so-called inking keys. Such keys are manipulated by the printer in order to apply the requisite differential quantities of ink across the width of the inking train, and hence ultimately to the sheet or web to be printed.
Use of conventional inking keys presents a number of problems, however. Thus, adjustment of the keys can be a time consuming process and may require considerable operator skill. While this problem may not be of paramount importance when long printing runs are contemplated, in the case of short runs the make-ready associated with inking key adjustments can represent a considerable cost to the printer, in terms of time and paper and ink wastage. The typical doctor blade is fabricated from a sheet of flexible spring metal. Ink key adjustment flexes the blade in the immediate area of that particular key. Experience has shown that adjustment of one key inevitably affects the performance of adjacent keys. Thus, many, many adjustments may be required in order to achieve quality printing results.
An adjustable fountain blade may also increase the horsepower requirements needed for rotation of the fountain roller. That is to say, many inks are highly viscous, gel-like substances, and in order to rotate the fountain roller against the adjustable blade, considerable horsepower can be needed.
Attempts have been made in the past to provide automatic control of the inking keys, making use of motorized adjustments and micro-processor control. However, these units are relatively expensive because of the need to provide multiple motors for the respective key adjustments.
It has also been suggested in the past to employ segmented fountain blades each including a respective adjustment key. This overcomes the noted problem of a given key adjustment affecting the performance of adjacent keys, but provides a relatively complex structure which is expensive and difficult to control. Moreover, the segmented blades are prone to leakage and can be difficult to clean.
For all of the foregoing reasons then, use of conventional fountain rollers and key-adjusted fountain blades presents considerable practical difficulties in terms of cost and operational efficiencies to the printer. There is therefore a decided need in the art for an improved inking system which completely eliminates the need for a fountain roller, associated blade, and adjustment keys while at the same time giving precise, readily adjustable inking control.